This invention has been created without the sponsorship or funding of any federally sponsored research or development program.
The present invention relates generally to a method of exposing and developing a fingerprint from the oxidized surface of an oxidizable metallic object and, specifically, to a method of exposing and developing a fingerprint from the rusted surface of a ferrous object.
Obtaining fingerprints from a smooth object is a well developed art in forensic science. When a person touches an object with the ends of his or her fingers, a discernable xe2x80x9cprintxe2x80x9d of the pattern of ridge lines on the person""s finger is left on the object. The tips of a person""s fingers contain perspiration from pores on the ridges and oils obtained from oily areas of the body such as the face. The grooves between the ridges have no pores. When a person touches an object, the sweat and oils at the ridges of the fingertips are deposited on the surface of the object in a pattern that is identical to the pattern of ridges. The sweat, which is 98% water (at least for eccrine type secretions), evaporates and the oil and sweat residue remains on the surface of the object.
When a metallic object is exposed to the elements, it oxidizes. In the case of a ferrous object, oxidization is in the form of rust. Rust is considered a hydrated iron(III) oxide of variable composition, Fe2O3.nH2O. The number of water molecules, n, associated with each Fe2O3 unit is variable. Since the grooves between the ridges do not deposit sweat and oil on a metallic object when it is touched, rust, in the case of a ferrous object, can start forming in the spaces between the ridge lines of a fingerprint and, eventually, bridge over the ridge lines.
When an oxidizable metallic object has been exposed to the elements for a sufficient length of time, an oxide, such as rust in the case of a ferrous object, covers the surface of the object. When this occurs, any fingerprints left on the surface of the object can no longer be seen or transferred to another planar surface by conventional methods for identification. At the present time, rust is removed from firearms in forensic laboratories by using ultrasonic cleaners in order to expose serial numbers. Solvents, which are also used with this method, are highly caustic, and destroy any fingerprints which are on the firearm. These and other difficulties experienced with identifying fingerprints on the oxidized surfaces of objects have been obviated by the present invention.
It is, therefore, a principal object of the present invention to provide a method of exposing a fingerprint on the surface of an object that has become oxidized, the exposure being sufficient so that the fingerprint can be identified.
A further object of the present invention is the provision of a method of producing a copy of a fingerprint which has been exposed on the oxidized surface of an object that has been oxidized.
With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended thereto.
This invention is a method of exposing a fingerprint on the surface of a metallic object which is covered with a layer of a metallic oxide such as rust. The metallic oxide is dissolved with a reagent which reacts with the metallic oxide. The dissolved metallic oxide is removed from the surface of the metallic object by washing with water to expose the fingerprint and a permanent copy is made of the fingerprint. More specifically, rust from a ferrous object is dissolved with an aqueous acid, the acid and dissolved rust is washed away with water and a photograph is taken of the exposed fingerprint. The rust can also be dissolved by treating the rust with a reagent containing an iron complexing anion or by spraying the rust with a Precision Brand Step #3 Aerosol Rust Inhibitor and Lubricant.